1. Field of the Invention
This invention relates generally to the field of lubricant additives, and more specifically relates to the field of extreme pressure additives suitable for addition to motor oils and other lubricants.
2. Description of the Prior Art
It is known that certain chlorine-based compounds, such as those chlorine derivates of paraffinic hydrocarbon compounds referred to as chlorinated paraffins, can serve as lubricant additives to improve the performance of the lubricant under extreme pressure. Under normal lubricating conditions, the two metal surfaces will be separated by a thin film of lubricant which provides the required reduction in friction. Under situations of extreme pressure between the two metal surfaces, all the liquid lubricant is forced from the area of contact between the surfaces. Where an extreme pressure additive such as chlorinated paraffin is present, however, it has been found that the resultant heat generated between the two surfaces causes chlorine atoms to be liberated from the additive and to combine with the surface metal, such as iron, to form a chloride, such as iron chloride. This surface coating of chloride has a much lower coefficient of friction than the dry metal surface. The iron chloride surface coating tends to fill in depressions in the surfaces, resulting in smoother surfaces at the point of interaction and reduced friction and wear.
Chlorinated paraffins have been used as extreme pressure additives in such applications as metal-working. However, the corrosive nature of chlorinated paraffins have made them generally unsuitable for use in internal combustion engine applications or other corrosionsensitive applications. Under heating, the chlorinated paraffins release hydrochloric acid, which is corrosive.